Structure-Composition-Property Relationships in Complex Intermetallic Phases: Experimental and Theoretical Studies

该项目涉及结合实验和理论方法来寻找和研究新的复杂金属间化合物，这些化合物将具有有趣的结构和磁性，并可能应用于环境友好型制冷剂和磁传感器。目标化合物由活性金属（钠、钾、锶、钡和稀土）与磁性元素（铁、钴、镍）和过渡后元素（铝、锗、铟、硅和锗）的组合组成：这样的化合物应该采用包含金属团簇的精美复杂结构，通过优化金属-金属键来控制，但也显示出通过与其轨道重叠耦合的交换相互作用（即磁热效应和磁致伸缩）产生有趣磁性的排列。这些研究将导致对金属间化合物如何形成和控制磁系统结构的因素的基本理解。如果我们成功地优化了磁热效应，我们可能会发现一种环境友好、经济可行的材料，可以在室温附近有效地制冷。青年科学家将学习空气敏感、高温合成、衍射和电子理论计算方面的最新技术。该项目旨在形成和研究不同金属元素之间的新化合物，称为金属间化合物。这些新化合物的一个组成部分将是磁性元素，如铁或钴，这将使我们能够探索新的化合物，以代替氯氟烃（“磁制冷”）作为制冷材料。这种化合物利用磁性来制冷，这是一个更有效的过程，而且这种材料也比目前的物质更环保。这项研究的一个重要的基本目标是了解控制金属间化合物形成和生长的因素，以便我们最终能够设计具有特定电性能或磁性质的材料。我们计划通过仔细合成、测量晶体中元素的结构和排列、测定它们的磁性和通过计算机建模来寻找新的金属间化合物，从而实现这一目标。参与该项目的学生将学习金属合成、表征和理论建模方面的最新技术。这个项目结合了实验和理论工作，将为这些学生在学术界（培养我们的下一代科学家和工程师）或工业界（在那里他们可以应用新技术制造新材料）的职业生涯做好准备。

This project involves combining experimental and theoretical approaches to search for and study new complex intermetallic compounds that will have interesting structural and magnetic properties with possible applications to environmentally friendly refrigerants and magnetic sensors. The compounds targeted consist of active metals (sodium, potassium, strontium, barium, and rare-earths) with combinations of magnetic elements (iron, cobalt, nickel) and the post-transition elements (aluminium, germanium, indium, silicon and germanium): such compounds should adopt beautifully complex structures involving metal clusters that are controlled by optimizing metal-metal bonding, but also showing arrangements giving interesting magnetic properties through exchange interactions coupled to their orbital overlaps, i.e., magnetocaloric effects and magnetostriction. These studies will lead to fundamental understanding of how intermetallic compounds form and the factors that control structure in magnetic systems. If we are successful to optimize the magnetocaloric effect, we may find a material effective for refrigeration near room temperature that is environmentally benign and economically feasible. Young scientists will learn state-of-the-art techniques in air-sensitive, high temperature synthesis, diffraction and in the theoretical calculation of electronic This project is designed to form and study new compounds between different metallic elements, called intermetallic compounds. One component of these new compounds will be magnetic elements, like iron or cobalt, which will allow us to probe new compounds to serve as materials for refrigeration in place of chlorofluorocarbons ("magnetic refrigeration"). Such compounds use magnetism to perform refrigeration, which is a more efficient process and the materials are also more environmentally friendly than current substances. An important fundamental goal of this research is to understand what factors control the formation and growth of intermetallic compounds, so that we may ultimately be able to design materials with specific electrical or magnetic properties. We plan to achieve this goal by searching for new intermetallic compounds through careful synthesis, through measurement of the structure and arrangement of elements in their crystals, through determination of their magnetic properties and through computer modeling. Students involved with this project will learn state-of-the-art techniques in metals synthesis, characterization and theoretical modeling. This project, which combines experimental and theoretical work, will prepare these students for careers in academia (for training our next generation of scientists and engineers) or in industry (where they can apply new techniques for the fabrication of new materials).